Unmanned Air Vehicles (UAVs) are performing an increasing number of roles in the military arena. Two of these roles are: Wide Area Surveillance (WAS) and Tactical Reconnaissance and Attack (TRA).
It is known that an aircraft optimised for the WAS role favours a high aspect ratio wing and one or more turboprop engines mounted in pods attached to the aircraft's airframe. In contrast, an aircraft optimised for the TRA role favours a low aspect ratio wing and a low bypass ratio turbofan mounted within the fuselage of the aircraft.
It has been proposed that a single aircraft could cover both WAS and TRA roles (a ‘multi-role’ aircraft) if it was designed to have interchangeable wings in order to vary the wing aspect ratio. However, at present, such an aircraft would have a single type of propulsion system which by necessity would have to be compromised for one or both of the WAS and TRA roles. As an example, such a compromise power plant might be a high bypass ratio turbofan.
A particular disadvantage of the prior art is that the propulsion system is non-optimum when the ‘multi-role’ aircraft is operated in either of the two proposed roles, i.e. WAS or TRA. This would translate into a performance deficit (for example, reduced range and/or endurance time) relative to an aircraft optimised for a single role.